From the very extensive list you have put forth, the clear champion IMHO and for the shooting that I do, is the very well reviewed Canon A-620. That is not to say that the balance of the cameras on your list are not well received, just that the Canon A-620 is clearly the winner and has a legion of very enthusiastic users.

well, i just want to take great pictures with the possibility for big zoom's. I have read that it is better to have a big resolution than a larger zoom (example: is better to have 7megapixels instead of 10x optical zoom because we can zoom the picture in the computer).

as a requirement i want the possibility for underwater pictures and the possibility of exchange (adding) other lens.

limitations of bugdet is relative. I have seen the canon a620 on sell by less than 300€ and also for about 450€.

Zooming in the computer is MUCH LESS effective than using the actual zoom on the camera. What happens is the pixels get further apart and pixelation sets in rather rapidly. With the introduction of the canon S-3, prices on the Canon S-2 have really decined. I would certainly take a good look at the Canon S-2, it is a great camera.